Affiliation:
1. Division of Neurophysiology and Neuropharmacology, N.I.M.R., The Ridgeway, Mill Hill, London NW7 1AA
2. Section of Vascular Biology, MRC Clinical Research Centre, Watford Road, Harrow HA1 3UJ, U.K.
Abstract
Single pig aortic endothelial cells in culture loaded with the Ca(2+)-sensitive fluorescent dye Indo-1 were stimulated with ATP (0.1-100 microM) or bradykinin (0.1-5.0 nM). Spiking or oscillations of [Ca2+]i were seen in approx. 50% of cells stimulated with either agonist. Non-spiking or transient responses in which [Ca2+]i returned to pre-stimulation levels rapidly 9120-250 s), or sustained responses in which [Ca2+]i remained elevated for many minutes, were seen in a further 20% of cells in each case, stimulated with either agonist. There was a marked variation between individual cells in the latency, magnitude, frequency and overall pattern of oscillations induced by ATP and bradykinin, although the patterns of response to bradykinin were less variable. In cells where repetitive spikes were seen, a relation between concentration of ATP and the latency of the response and the frequency of spiking was evident. Effects of removal of extracellular Ca2+, elevation of extracellular K+ concentration (35 or 70 mM) or exposure to phorbol 12,13-dibutyrate or 1,2-dioctanoyl-sn-glycerol were tested on the spiking Ca2+ responses. Each of these procedures reversibly slowed or prevented Ca2+ spiking evoked by ATP or bradykinin. In contrast, the inactive phorbol ester 4 alpha-phorbol didecanoate had no effect on Ca2+ spiking evoked by these hormones. Our results thus indicate that the responses of single cells to ATP or bradykinin exhibit marked heterogeneity, and suggest that secretory events driven by extracellular Ca2+ may be regulated by repetitive spikes or oscillations of Ca2+.
Subject
Cell Biology,Molecular Biology,Biochemistry
Cited by
30 articles.
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